Anodic electrochemistry of free and coordinated 1,1′-bis(di-tert-butylphosphino)ferrocene

The electrochemistry of 1,1'-bis(di-tert-butylphosphino) ferrocene (dtbpf) was examined in methylene chloride with tetrabutylammonium hexafluorophosphate as the supporting electrolyte. Two new complexes in which dtbpf was bound to a transition metal were prepared and characterized. The two new complexes as well as two previously reported complexes were analyzed by cyclic voltammetry. In addition, the chalcogenids, dtbpfS(2) and dtbpfSe(2), were prepared and characterized by NMR and the structure of dtbpfSe(2) was determined. The oxidation of dtbpfS(2) is a simple one-electron process due to the presence of the iron center. In contrast, the oxidation of dtbpfSe(2) is electrochemically irreversible and appears to proceed by an EE mechanism. Chemical oxidation of dtbpfSe(2) resulted in the formation of [dtbpfSe(2)][BF4](2), in which a Se-Se bond formed. This compound was characterized by P-31 NMR and X-ray crystallography. A detailed analysis of the electrochemistry suggests that the oxidation of dtbpfSe(2) occurs by two separate one-electron processes. In addition, formation of the Se-Se bond was reversible.